The Harry Potter epilogue takes place in 2017, which means not only have those kids already seen Pacific Rim, but they have been subjected to Pacific Rim 2.

this is probably what “all was well” was referring to. 

6

On December 18, 1941, Hitler attended a Christmas party in Munich. These images were captured by Hugo Jaeger, Hitler’s personal photographer, who buried the photographs near Munich after the war, fearing they might be confiscated. After the war, Jaeger retrieved the pictures and sold them to ‘Life Magazine’ who of course, used them for anti-Hitler propaganda purposes. (source)